Abstract : A method and device for precisely driving a rotary object includes a motor mounted in a housing and a reduction device comprising first and second harmonic drives, which connect the motor to the object to be driven via an output shaft. The output shaft is connected to the object to be driven via an adapter cup and a bellows which is stiff in torsion but which tolerates misalignments between the drive device and the object. All elements are designed to maximize stiffness and precision and to minimize backlash while maintaining maximum concentricity between the elements.